Change the logic for the default for MaxMemInQueues
If we can't detect the physical memory, the new default is 8 GB on 64-bit architectures, and 1 GB on 32-bit architectures. If we *can* detect the physical memory, the new default is CLAMP(256 MB, phys_mem * 0.75, MAX_DFLT) where MAX_DFLT is 8 GB on 64-bit architectures and 2 GB on 32-bit architectures. You can still override the default by hand. The logic here is simply trying to choose a lower default value on systems with less than 12 GB of physical RAM.